In recent years, in conjunction with development of industries and multipoint progress of manufacturing industries, air pollution on a global scale has been feared. For example, respiratory diseases due to particulate matter in suspension (Suspended Particulate Matter: SPM or particulate matter: PM 2.5) or ground level ozone can be mentioned. According to an environmental outlook to 2050 published in 2012 by the Organization for Economic Co-operation and Development (OECD) which is an international organization, with regard to children early deaths, aspiratory diseases due to such atmospheric contaminants will increase over the next few decades. In other words, as causes of global health problems, air pollution is a matter of concern. Such air pollution is expected to be higher in China or developing countries in South Asia, etc.
Also in our country, with respect to suspended particulate matter and photochemical oxidants (as principal substances, ozone and the like are included), locations showing an excess over environmental standards have been appearing.
Measuring atmospheric contaminants, such as suspended particulate matter and photochemical oxidants, and taking countermeasures based on measurement results is necessary.
For example, in our country, environmental monitoring stations at which each municipality measures atmospheric contaminants are set up throughout the country and a system connecting each of the environmental monitoring stations is used to monitor air pollution. Specifications of a measurement device for measuring atmospheric contaminants are determined under official regulations, and accuracy of the measurement results is secured.
For example, to measure suspended particulate matter, such as SPM or PM 2.5, the measurement device which is of a β-ray absorption type is used.    Patent literature 1: Japanese Unexamined Patent Publication (Kokai) No. 2002-501187    Patent literature 2: Japanese Unexamined Patent Publication (Kokai) No. 2007-147437    Patent literature 3: Japanese Unexamined Patent Publication (Kokai) No. 2006-3090